Electrostatic ink compositions and scratch-off structures

ABSTRACT

Disclosed herein is an electrostatic ink composition comprising a component selected from a fatty acid ester having a plurality of hydroxyl substituents and a fatty acid amide having a plurality of hydroxyl substituents. Also described herein are scratch-off structures and methods for producing them.

PRIORITY CLAIM

The present application is a continuation of U.S. patent applicationSer. No. 16/307,412, filed on Dec. 5, 2018, which is a U.S. NationalStage Application under 35 U.S.C. 371 of PCT/EP2016/073468, filed onSep. 30, 2016, each of which is incorporated herein by reference in itsentirety.

BACKGROUND

Scratch-off structures can be objects that have a layer comprisinginformation and an overlying layer obscuring the information, which canbe scratched off to reveal the information, but is typically resistantto normal abrasion. The information can vary in a collection ofscratch-off structures, and they can be used for many purposes, such asgaming (e.g., in scratch cards used in lottery gaming) or authenticationpurposes (e.g., on a bank card).

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 schematically depicts a cross-section of an example of ascratch-off structure before (a) and after (b) the layers have beenscratched off.

FIG. 2(a) to (c) shows schematically an example of a scratch-offstructure being produced and then having a portion scratched off toreveal information.

FIG. 3 shows the results of the scratchability test by using the Taberapparatus in Example 3.

FIG. 4 shows the results of the scratchability tests in Example 4.

DETAILED DESCRIPTION

Before the present disclosure is disclosed and described, it is to beunderstood that this disclosure is not limited to the particularcompositions, process steps and materials disclosed herein because suchprocess steps and materials may vary somewhat. It is also to beunderstood that the terminology used herein is used for the purpose ofdescribing particular embodiments. The terms are not intended to belimiting because the scope is intended to be limited by the appendedclaims and equivalents thereof.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used herein, “carrier fluid”, “carrier liquid,” “carrier,” or“carrier vehicle” refers to the fluid in which solid components, such aspigment particles (if present), thermoplastic resin, charge directorsand other additives, can be dispersed to form a liquid electrostaticcomposition or electrophotographic composition. The carrier liquids mayinclude a mixture of a variety of different agents, such as surfactants,co-solvents, viscosity modifiers, and/or other possible ingredients.

As used herein, “electrostatic ink composition” or “liquidelectrophotographic composition” generally refers to an ink compositionthat is typically suitable for use in an electrostatic printing process,sometimes termed an electrophotographic printing process. It maycomprise particles comprising a thermoplastic resin. The electrostaticink composition comprising the release additive (which may be atransparent electrostatic ink composition and used to form the thirdlayer described herein) and/or the coloured electrostatic inkcomposition (which may be used to form the fourth layer describedherein) may be a liquid electrostatic ink composition, in whichparticles comprising a resin are suspended in a carrier liquid. Thetransparent and/or the coloured electrostatic ink composition may be ina dry toner form, in which the toner particles are in a dry, butflowable form. In a coloured electrostatic ink composition, theparticles may further include a colourant. In the transparentelectrostatic ink composition, the particles may lack or substantiallylack a colourant, but may further comprise the release additive asdescribed herein. The particles comprising resin will typically becharged or capable of developing charge in an electric field, such thatthey display electrophoretic behaviour. A charge director may be presentto impart a charge to the pigment particles having resin thereon.

As used herein, “co-polymer” refers to a polymer that is polymerizedfrom at least two monomers.

As used herein, “melt flow rate” generally refers to the extrusion rateof a resin through an orifice of defined dimensions at a specifiedtemperature and load, usually reported as temperature/load, e.g., 190°C./2.16 kg. Flow rates can be used to differentiate grades or provide ameasure of degradation of a material as a result of molding. In thepresent disclosure, “melt flow rate” is measured per ASTM D1238-04cStandard Test Method for Melt Flow Rates of Thermoplastics by ExtrusionPlastometer, as known in the art. If a melt flow rate of a particularpolymer is specified, unless otherwise stated, it is the melt flow ratefor that polymer alone, in the absence of any of the other components ofthe composition.

As used herein, “acidity,” “acid number,” or “acid value” refer to themass of potassium hydroxide (KOH) in milligrams that neutralizes onegram of a substance. The acidity of a polymer can be measured accordingto standard techniques, for example, as described in ASTM D1386. If theacidity of a particular polymer is specified, unless otherwise stated,it is the acidity for that polymer alone, in the absence of any of theother components of the composition.

As used herein, “melt viscosity” generally refers to the ratio of shearstress to shear rate at a given shear stress or shear rate. Testing isgenerally performed by using a capillary rheometer. A plastic charge isheated in the rheometer barrel and is forced through a die with aplunger. The plunger is pushed either by a constant force or at aconstant rate depending on the equipment. Measurements are taken oncethe system has reached steady-state operation. One method used ismeasuring Brookfield viscosity at 140° C., units are mPa·s or cPoise, asknown in the art. Alternatively, the melt viscosity can be measuredusing a rheometer, for example, a commercially available AR-2000Rheometer from Thermal Analysis Instruments, using the geometry of: 25mm steel plate—standard steel parallel plate, and finding the plate overplate rheometry isotherm at 120° C., 0.01 Hz shear rate. If the meltviscosity of a particular polymer is specified, unless otherwise stated,it is the melt viscosity for that polymer alone, in the absence of anyof the other components of the composition.

A certain monomer may be described herein as constituting a certainweight percentage of a polymer. This indicates that the repeating unitsformed from the said monomer in the polymer constitute said weightpercentage of the polymer.

If a standard test is mentioned herein, unless otherwise stated, theversion of the test to be referred to is the most recent at the time offiling this patent application.

As used herein, “electrostatic printing” or “electrophotographicprinting” generally refers to the process that provides an image that istransferred from a photo imaging substrate either directly or indirectlyvia an intermediate transfer member to a print substrate. As such, theimage is not substantially absorbed into the photo imaging substrate onwhich it is applied. Additionally, “electrophotographic printers” or“electrostatic printers” generally refer to those printers capable ofperforming electrophotographic printing or electrostatic printing, asdescribed above. “Liquid electrophotographic printing” or “liquidelectrostatic printing” is a specific type of electrophotographicprinting where a liquid composition is employed in theelectrophotographic process rather than a powder toner. An electrostaticprinting process may involve subjecting the electrostatic composition toan electric field, for example, an electric field having a fieldgradient of 50-400 V/μm, or more, in some examples 600-900 V/μm, ormore.

As used herein, “NVS” is an abbreviation of the term “non-volatilesolids”.

As used herein, the term “about” is used to provide flexibility to anumerical range endpoint by providing that a given value may be a littleabove or a little below the endpoint to allow for variation in testmethods or apparatus. The degree of flexibility of this term can bedictated by the particular variable and would be within the knowledge ofthose skilled in the art to determine based on experience and theassociated description herein.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such a list should be construed asa de facto equivalent of any other member of the same list solely basedon their presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not just the numerical valuesexplicitly recited as the limits of the range, but also to include allthe individual numerical values or sub-ranges encompassed within thatrange as if each numerical value and sub-range is explicitly recited. Asan illustration, a numerical range of “about 1 wt % to about 5 wt %”should be interpreted to include not just the explicitly recited valuesof about 1 wt % to about 5 wt %, but also include individual values andsubranges within the indicated range. Thus, included in this numericalrange are individual values such as 2, 3.5, and 4 and sub-ranges such asfrom 1-3, from 2-4, and from 3-5, and so forth. This same principleapplies to ranges reciting a single numerical value. Furthermore, suchan interpretation should apply regardless of the breadth of the range orthe characteristics being described.

As used herein, and unless stated otherwise, wt % values are to be takenas referring to a weight-for-weight (w/w) percentage of solids in theink composition, and not including the weight of any carrier fluidpresent.

Unless otherwise stated, any feature described herein can be combinedwith any aspect or any other feature described herein.

Herein is disclosed an electrostatic ink composition. The electrostaticink composition may comprise:

-   -   a component selected from a fatty acid ester having a plurality        of hydroxyl substituents and a fatty acid amide having a        plurality of hydroxyl substituents.

Herein is also disclosed a method for producing a scratch-off structure.The method may comprise:

-   -   providing a substrate having a first layer showing information        thereon, and a second layer overlying the first layer, the        second layer comprising a polymeric film and being substantially        transparent;    -   electrostatically printing a third layer over the second layer,        the third layer comprising an electrostatic ink, which may be a        transparent or a coloured electrostatic ink, wherein the        electrostatic ink comprises a component selected from a fatty        acid ester having a plurality of hydroxyl substituents and a        fatty acid amide having a plurality of hydroxyl substituents;        and, in some examples,    -   disposing a fourth layer on the third layer, the fourth layer        being coloured.

Herein is disclosed a scratch-off structure. The scratch-off structuremay comprise the following layers in order:

-   -   a substrate having a first layer showing information thereon,    -   a second layer comprising a polymeric film and being        substantially transparent;    -   a third layer comprising an electrostatic ink, which may be a        transparent or a coloured electrostatic ink, wherein the        electrostatic ink comprises a component selected from a fatty        acid ester having a plurality of hydroxyl substituents and a        fatty acid amide having a plurality of hydroxyl substituents;        and, in some examples,    -   a fourth layer, wherein the fourth layer is coloured.

Also disclosed herein is a collection of scratch-off structures. In someexamples, at least some of the scratch-off structures comprise thefollowing layers in order:

-   -   a substrate having a first layer showing information thereon,    -   a second layer comprising a polymeric film and being        substantially transparent;    -   a third layer comprising an electrostatic ink, which may be a        transparent or a coloured electrostatic ink, wherein the        electrostatic ink comprises a component selected from a fatty        acid ester having a plurality of hydroxyl substituents and a        fatty acid amide having a plurality of hydroxyl substituents;        and, in some examples,    -   a fourth layer, wherein the fourth layer is coloured, and        wherein the information of the first layer of at least two of        the scratch-off structures is different to one another.

The present disclosure relates to an electrostatic ink composition,which can be used in scratch-off structures and a method to producescratch-off structures by using the electrostatic ink composition, aswell as new scratch-off structures formed therefrom. Examples of theelectrostatic ink composition allow the production of very effectivescratch cards and other scratch-off structures. Some examples allow thevariable information, the transparent electrostatic ink and theoverlying coloured layer to all be printed by using electrostaticprinting, making production of the scratch cards very fast andefficient. The inclusion of a particular additive, namely a componentselected from a fatty acid ester having a plurality of hydroxylsubstituents and a fatty acid amide having a plurality of hydroxylsubstituents, in the transparent electrostatic ink reduces the adhesionbetween transparent electrostatic ink and a polymeric film. Thisadhesion has been found to be sufficiently weak that it allows removalof the transparent electrostatic ink and overlying layer(s) byscratching, yet it is sufficiently strong that gentle abrasion (e.g., instacking or handling the structures) will not remove the transparentelectrostatic ink and overlying layers.

Electrostatic Ink Composition

The electrostatic ink composition comprises a component selected from afatty acid ester having a plurality of hydroxyl substituents and a fattyacid amide having a plurality of hydroxyl substituents. Theelectrostatic ink composition may or may not comprise a colorant. Insome examples, the electrostatic ink composition comprises a colorant,which may be a colorant selected from black, magenta, cyan, yellow andwhite colorant.

In some examples, the electrostatic ink composition is a liquidelectrostatic ink composition. In some examples, the liquidelectrostatic ink composition may comprise:

-   -   a. a resin;    -   b. a carrier liquid; and    -   c. in some examples, a charge director and/or charge adjuvant.

The electrostatic ink composition may be a transparent electrostatic inkcomposition. The transparent electrostatic ink, which may also be termeda transparent electrostatic ink composition, may comprise athermoplastic resin. It may further comprise a charge adjuvant and/or acharge director. The transparent electrostatic ink composition does notcontain any pigment, or substantially lacks pigment and thus is apigment-free composition or substantially pigment-free composition. Thetransparent electrostatic ink composition may otherwise be termed acolourless electrostatic ink composition or a colourless varnish fordigital printing. The transparent electrostatic ink composition maycomprise 5 wt % solids or less of colorant, in some examples, 3 wt %solids or less of colorant, in some examples, 1 wt % solids or less ofcolorant. “Colourant” may be a material that imparts a colour to the inkcomposition. As used herein, “colourant” includes pigments and dyes,such as those that impart colours, such as black, magenta, cyan, yellowand white to an ink. As used herein, “pigment” generally includespigment colourants, magnetic particles, aluminas, silicas, and/or otherceramics or organometallics. Thus, though the present descriptionprimarily exemplifies the use of pigment colourants, the term “pigment”can be used more generally to describe not only pigment colourants, butalso other pigments such as organometallics, ferrites, ceramics, and soforth.

The resin, which may be a thermoplastic resin, and the componentselected from a fatty acid ester having a plurality of hydroxylsubstituents and a fatty acid amide having a plurality of hydroxylsubstituents together may constitute at least 85 wt % of the solids ofthe electrostatic ink composition, in some examples, at least 90 wt % ofthe solids of the electrostatic ink composition, in some examples, 95 wt% of the solids of the electrostatic ink composition.

The component selected from a fatty acid ester having a plurality ofhydroxyl substituents and a fatty acid amide having a plurality ofhydroxyl substituents may constitute at least 1 wt % of the solids ofthe electrostatic ink composition, in some examples, at least 2 wt % ofthe solids, in some examples, at least 3 wt % of the solids, in someexamples, at least 5 wt % of the solids, in some examples, at least 7 wt% of the solids of the electrostatic ink composition.

The component selected from a fatty acid ester having a plurality ofhydroxyl substituents and a fatty acid amide having a plurality ofhydroxyl substituents may constitute 30 wt % or less of the solids ofthe electrostatic ink composition, in some examples, 25 wt % or less ofthe solids, in some examples, 20 wt % or less of the solids, in someexamples, 18 wt % or less of the solids, in some examples, 17 wt % orless of the solids of the electrostatic ink composition.

The component selected from a fatty acid ester having a plurality ofhydroxyl substituents and a fatty acid amide having a plurality ofhydroxyl substituents may constitute from 1 wt % to 30 wt % of thesolids of the electrostatic ink composition, in some examples from 3 wt% to 30 wt %, in some examples 5 wt % to 30 wt %, in some examples 5 wt% to 25 wt %, in some examples 5 wt % to 20 wt % of the solids of theelectrostatic ink composition, in some examples 5 wt % to 15 wt % of thesolids of the electrostatic ink composition, in some examples 5 wt % to10 wt % of the solids of the electrostatic ink composition, in someexamples 10 wt % to 20 wt % of the solids of the electrostatic inkcomposition, in some examples 15 wt % to 20 wt % of the solids of theelectrostatic ink composition.

The electrostatic ink composition comprising the component selected froma fatty acid ester having a plurality of hydroxyl substituents and afatty acid amide having a plurality of hydroxyl substituents may furthercomprise at least one additive such as surfactants, viscosity modifiers,emulsifiers and the like.

Fatty Acid Ester or a Fatty Acid Amide Having a Plurality of HydroxylSubstituents

The electrostatic ink composition comprises a component selected from afatty acid ester having a plurality of hydroxyl substituents and a fattyacid amide having a plurality of hydroxyl substituents. In someexamples, the electrostatic ink composition comprises a fatty acid esterhaving a plurality of hydroxyl substituents. In some examples, theelectrostatic ink composition comprises a fatty acid amide having aplurality of hydroxyl substituents. For brevity, ‘the component selectedfrom a fatty acid ester having a plurality of hydroxyl substituents anda fatty acid amide having a plurality of hydroxyl substituents’ willalso be termed herein a release additive. In some examples, the releaseadditive may comprise a mixture of fatty acid esters and/or a mixture offatty acid amides. In some examples, the mixture of fatty acid estersmay be derived from a vegetable oil, for example, castor oil.

In some examples, a plurality of hydroxyl substituents may comprise atleast 2 hydroxyl substituents, in some examples at least 3 hydroxylsubstituents.

In some examples, the fatty acid ester or fatty acid amide comprises atleast one carbon chain comprising 4 to 40 carbon atoms, in someexamples, 4 to 28 carbon atoms, in some examples, 6 to 26 carbon atoms,in some examples, 10 to 24 carbon atoms, in some examples, 12 to 20carbon atoms, in some examples, 14 to 20 carbon atoms.

In some examples, the fatty acid ester or fatty acid amide may compriseor be derived from (e.g. formed by esterification or amidation of)saturated or unsaturated fatty acids, i.e. the fatty acid ester or fattyacid amide comprises a saturated or unsaturated carbon chain. In someexamples, the fatty acid ester or fatty acid amide may comprise or bederived from (e.g. formed by esterification or amidation of) saturatedfatty acids, i.e. comprise a saturated carbon chain.

In some examples, the fatty acid ester or fatty acid amide may compriseor be derived from (e.g. formed by esterification or amidation of)straight-chain, branched or cyclic fatty acids, i.e. having astraight-chain, branched or cyclic carbon chain. In some examples, thefatty acid ester or fatty acid amide may comprise or be derived from(e.g. formed by esterification or amidation of) straight-chain orbranched fatty acids. In some examples, the fatty acid ester or fattyacid amide may comprise or be derived from (e.g. formed byesterification or amidation of) straight-chain fatty acids.

In some examples, the fatty acid ester is producible by esterificationof at least one fatty acid with an alcohol. In some examples, the fattyacid ester is producible by esterification of a plurality fatty acidswith a polyol. In some examples, the fatty acid ester is producible byesterification of two fatty acids with an alcohol having at least twohydroxy groups. In some examples, the fatty acid ester is producible byesterification of three fatty acids with an alcohol having at leastthree hydroxy groups.

In some examples, the fatty acid ester may comprise or be derived from aplurality of fatty acids, which may be the same or different. In otherwords, each fatty acid ester molecule can contain at least two differenttypes of carbon chain, each of which is derived from a different fattyacid.

In some examples, the fatty acid ester may be a glyceride, in someexamples, a monoglyceride, a diglyceride or a triglyceride. In someexamples, the fatty acid ester is a di- or triglyceride. In someexamples, the fatty acid ester is a triglyceride.

In some examples, each of the plurality of hydroxyl substituents may besubstituents on one carbon chain. In other words, in some examples, thefatty acid ester or fatty acid amide may comprise a carbon chain havinga plurality of hydroxyl substituents.

In some examples, each of the plurality of hydroxyl substituents may besubstituents on different carbon chains. In other words, in someexamples, the fatty acid ester or fatty acid amide may comprise aplurality of carbon chains, at least two of which each has at least onehydroxyl substituent.

In some examples, the fatty acid ester is a di- or triglyceride and eachof the fatty acid chains (i.e. the carbon chains of the fatty acid) onthe same molecule may be the same or different. In some examples, thefatty acid ester is a di- or triglyceride and each of the fatty acidchains (i.e. the carbon chains of the fatty acid) comprises at least onehydroxyl substituent. In some examples, the fatty acid ester is a di- ortriglyceride and each of the fatty acid chains comprises one hydroxylsubstituent.

In some examples, the fatty acid ester is a mono-, di- or triglycerideformed from saturated or unsaturated fatty acids. In some examples, thefatty acid ester is a mono-, di- or triglyceride formed from saturatedfatty acids.

In some examples, the fatty acid ester is a mono-, di- or triglyceridethat may comprise may comprise or be derived from straight-chain,branched or cyclic fatty acids or a mixture thereof. In some examples,the fatty acid ester is a mono-, di- or triglyceride that may compriseor be derived from a straight-chain or branched fatty acid or a mixturethereof. In some examples, the fatty acid ester is a mono-, di- ortriglyceride comprising or derived from straight-chain fatty acids.

In some examples, the fatty acid ester may comprise an esterifiedmonohydroxy fatty acid. In some examples, the fatty acid ester maycomprise an esterified dihydroxy fatty acid.

In some examples, the fatty acid ester may comprise an esterifiedmonohydroxyfatty acid, wherein the fatty acid may be selected fromhydroxycaprylic acid, hydroxycapric acid, hydroxylauric acid,hydroxymyristic acid, hydroxypalmitic acid, hydroxystearic acid,hydroxyarachidic acid, hydroxybehenic acid, hydroxycerotic acid; and, insome examples, the esterified fatty acid may be a diglyceride or atriglyceride, i.e. the ester of glycerol and two of the fatty acids orthree of the fatty acids, respectively. In some examples the fatty acidester may comprise an esterified dihydroxyfatty acid, and the fatty acidmay be selected from dihydroxycaprylic acid, dihydroxycapric acid,dihydroxylauric acid, dihydroxymyristic acid, dihydroxypalmitic acid,dihydroxystearic acid, dihydroxyarachidic acid, dihydroxybehenic acid,dihydroxycerotic acid; and, in some examples, the esterified fatty acidmay be a monoglyceride, a diglyceride or a triglyceride, i.e. the esterof glycerol and one of the fatty acids, the ester of glycerol and two ofthe fatty acids or the ester of glycerol and three of the fatty acids,respectively.

In some examples, the fatty acid ester may comprise an ester of a fattyacid selected from ricinoleic acid, 12-hydroxystearic acid (i.e.,hydrogenated ricinoleic acid), 10-hydroxystearic acid, 3-hydroxystearicacid, 12-hydroxylauric acid, 16-hydroxpalmitic acid, 2-hydroxypalmiticacid or 3-hydroxypalmitic acid, and, in some examples, the esterifiedfatty acid may be a diglyceride or a triglyceride, i.e. the ester ofglycerol and two of the fatty acids or the ester of glycerol and threeof the fatty acids, respectively. In some examples, the fatty acid estermay be selected from an an 9,10-dihydroxystearic acid,9,12-dihydroxystearic acid and, in some examples, the esterified fattyacid may be a monoglyceride, a diglyceride or a triglyceride, i.e. theester of glycerol and one of the fatty acids, the ester of glycerol andtwo of the fatty acids or the ester of glycerol and three of the fattyacids, respectively. In some examples, the fatty acid ester may comprisea mixture of any of these esterified fatty acids.

In some examples, the fatty acid ester may comprise an esterifiedsaturated hydroxyl fatty acid, wherein the hydroxyl fatty acid may beselected from 2-hydroxyvaleric acid, 2-hydroxycaproic acid,6-hydroxycaproic acid, 2-hydroxyenanthic acid, 7-hydroxyenanthic acid,2-hydroxycaprylic acid, 3-hydroxycaprylic acid, 8-hydroxycaprylic acid,2-hydroxypelargonic acid, 3-hydroxypelargonic acid, 9-hydroxypelargonicacid, 2-hydroxycapric acid, 3-hydroxycapric acid, 10-hydroxycapric acid,2-hydroxyundecanoic acid, 3-hydroxyundecanoic acid, 11-hydroxyundecanoicacid, 2-hydroxylauric acid, 3-hydroxylauric acid, 12-hydroxylauric acid,2-hydroxytridecanoic acid, 3-hydroxytridecanoic acid,13-hydroxytridecanoic acid, 2-hydroxymyristic acid, 3-hydroxymyristicacid, 14-hydroxymyristic acid, 2-hydroxpentadecanoic acid,3-hydroxypentadecanoic acid, 15-hydroxypentadecanoic acid,2-hydroxpalmitic acid, 3-hydroxypalmitic acid, 16-hydroxypalmitic acid,2-hydroxymargaric acid, 3-hydroxymargaric acid, 17-hydroxymargaric acid,2-hydroxystearic acid, 3-hydroxystearic acid, 4-hydroxystearic acid,5-hydroxystearic acid, 6-hydroxystearic acid, 7-hydroxystearic acid,8-hydroxystearic acid, 9-hydroxystearic acid, 10-hydroxystearic acid,11-hydroxystearic acid, 12-hydroxystearic acid, 13-hydroxystearic acid,14-hydroxystearic acid, 15-hydroxystearic acid, 16-hydroxystearic acid,17-hydroxystearic acid, 18-hydroxystearic acid, 2-hydroxynonadecanoicacid, 3-hydroxynonadecanoic acid, 19-hydroxynonadecanoic acid,2-hydroxyarachic acid, 3-hydroxyarachic acid, 20-hydroxyarachic acid,3-hydroxyheneicosanoic acid, 21-hydroxyheneicosanoic acid,2-hydroxybehenic acid, 3-hydroxybehenic acid, 3-hydroxytricosanoic acid,2-hydroxylignoceric acid, 3-hydroxylignoceric acid,2-hydroxyhexacosanoic acid, 2-hydroxytriacontanoic acid,2-hydroxytetratriacontanoic acid, 2-methyl-2-hydroxyenanthic acid,2-methyl-3-hydroxypelargonic acid, 3-methyl-3-hydroxypelargonic acid,2-methyl-3-hydroxycapric acid, 2-methyl-3-hydroxyundecanoic acid,3-methyl-3-hydroxyundecanoic acid, 2-methyl-2-hydroxylauric acid,2-methyl-3-hydroxylauric acid, 2-methyl-2-hydroxytridecanoic acid,2-methyl-3-hydroxytridecanoic acid, 3-methyl-3-hydroxytridecanoic acid,2-methyl-2-hydroxymyristic acid, 2-methyl-3-hydroxymyristic acid,2-methyl-2-hydroxypentadecanoic acid, 2-methyl-3-hydroxypentadecanoicacid, 3-methyl-3-hydroxypentadecanoic acid, 2-methyl-2-hydroxypalmiticacid, 2-methyl-2-hydroxymargaric acid, 2-methyl-3-hydroxymargaric acid,3-methyl-3-hydroxymargaric acid, 2-methyl-2-hydroxystearic acid,2-methyl-2-hydroxynonadecanoic acid, 2-methyl-2-hydroxynonadecanoicacid, and 3-methyl-3-hydroxynonadecanoic acid, and, in some examples,the esterified fatty acid may be a monoglyceride, a diglyceride or atriglyceride, i.e. the ester of glycerol and one of the fatty acids, theester of glycerol and two of the fatty acids or the ester of glyceroland three of the fatty acids, respectively.

In some examples, the fatty acid ester may comprise a vegetable oil or ahydrogenated vegetable oil. In some examples, the fatty acid ester maybe selected from castor oil or castor oil, lesquerella oil, cosmos oil,and hydrogenated oils thereof. In some examples, the fatty acid estermay comprise a hydrogenated castor oil.

In some examples, the fatty acid amide may be a primary amide, asecondary amide or a tertiary amide. In some examples, the fatty acidamide may be a secondary amide or a tertiary amide. In some examples,the fatty acid amide may be a ceramide.

The component selected from a fatty acid ester having a plurality ofhydroxyl substituents and a fatty acid amide having a plurality ofhydroxyl substituents may be the reaction product resulting from thereaction between a fatty acid ester having a plurality of hydroxylsubstituents, such as a hydrogenated castor oil, and an amine, such asan aliphatic diamine, which may be selected from 1,2-ethanediamine,1,3-propane-diamine and 1,6-hexanediamine.

Liquid Carrier

In some examples, for example when printing, the electrostatic inkcomposition comprising the release additive and/or the colouredelectrostatic ink composition of the fourth layer comprises a liquidcarrier. The liquid carrier for the electrostatic ink compositioncomprising the release additive (which may be a transparentelectrostatic ink composition) and the liquid carrier for the colouredelectrostatic ink composition may be the same as one another ordifferent from one another. Generally, the liquid carrier can act as adispersing medium for the other components in the electrostatic inkcomposition. For example, the liquid carrier can comprise or be ahydrocarbon, silicone oil, vegetable oil, and so forth. The liquidcarrier can include, but is not limited to, an insulating, non-polar,non-aqueous liquid that can be used as a medium for toner particles. Theliquid carrier can include compounds that have a resistivity in excessof about 10⁹ ohm·cm. The liquid carrier may have a dielectric constantbelow about 5, in some examples below about 3. The liquid carrier caninclude, but is not limited to, hydrocarbons. The hydrocarbon caninclude, but is not limited to, an aliphatic hydrocarbon, an isomerizedaliphatic hydrocarbon, branched chain aliphatic hydrocarbons, aromatichydrocarbons, and combinations thereof. Examples of the liquid carriersinclude, but are not limited to, aliphatic hydrocarbons, isoparaffiniccompounds, paraffinic compounds, dearomatized hydrocarbon compounds, andthe like. In particular, the liquid carriers can include, but are notlimited to, Isopar-G™, Isopar-H™, Isopar-L™, Isopar-M™, Isopar-K™,Isopar-V™, Norpar 12™, Norpar 13™, Norpar 15™, Exxol D40™, Exxol D80™,Exxol D100™, Exxol D130™, and Exxol D140™ (each sold by EXXONCORPORATION); Teclen N-16™, Teclen N-20™, Teclen N-22™, NissekiNaphthesol L™, Nisseki Naphthesol M™, Nisseki Naphthesol H™, #0 SolventL™, #0 Solvent M™, #0 Solvent H™, Nisseki Isosol 300™, Nisseki Isosol400™, AF-4™, AF-5™, AF-6™ and AF-7™ (each sold by NIPPON OILCORPORATION); IP Solvent 1620™ and IP Solvent 2028™ (each sold byIDEMITSU PETROCHEMICAL CO., LTD.); Amsco OMS™ and Amsco 460™ (each soldby AMERICAN MINERAL SPIRITS CORP.); and Electron, Positron, New II,Purogen HF (100% synthetic terpenes) (sold by ECOLINK™)

Before electrostatic printing, the liquid carrier can constitute about20% to 99.5% by weight of the electrostatic ink composition comprisingthe component selected from a fatty acid ester having a plurality ofhydroxyl substituents and a fatty acid amide having a plurality ofhydroxyl substituents and/or the coloured electrostatic ink composition,in some examples, 50% to 99.5% by weight of the electrostatic inkcomposition the component selected from a fatty acid ester having aplurality of hydroxyl substituents and a fatty acid amide having aplurality of hydroxyl substituents and/or the coloured electrostatic inkcomposition. Before printing, the liquid carrier may constitute about 40to 90% by weight of the electrostatic ink composition comprising thecomponent selected from a fatty acid ester having a plurality ofhydroxyl substituents and a fatty acid amide having a plurality ofhydroxyl substituents and/or the coloured electrostatic ink composition.Before printing, the liquid carrier may constitute about 60% to 80% byweight of the electrostatic ink composition comprising the componentselected from a fatty acid ester having a plurality of hydroxylsubstituents and a fatty acid amide having a plurality of hydroxylsubstituents and/or the coloured electrostatic ink composition. Beforeprinting, the liquid carrier may constitute about 90% to 99.5% by weightof the electrostatic ink composition comprising the component selectedfrom a fatty acid ester having a plurality of hydroxyl substituents anda fatty acid amide having a plurality of hydroxyl substituents and/orthe coloured electrostatic ink composition, in some examples, 95% to 99%by weight of the electrostatic ink composition comprising the componentselected from a fatty acid ester having a plurality of hydroxylsubstituents and a fatty acid amide having a plurality of hydroxylsubstituents and/or the coloured electrostatic ink composition.

The electrostatic ink composition comprising the component selected froma fatty acid ester having a plurality of hydroxyl substituents and afatty acid amide having a plurality of hydroxyl substituents and/or thecoloured electrostatic ink, when electrostatically printed, may besubstantially free from liquid carrier. In an electrostatic printingprocess and/or afterwards, the liquid carrier may be removed, forexample, by an electrophoresis processes during printing and/orevaporation, such that substantially just solids are transferred to theprint substrate (in the present context, when printed on the second orthird layer, as appropriate). Substantially free from liquid carrier mayindicate that the ink printed on the print substrate contains less than5 wt % liquid carrier, in some examples, less than 2 wt % liquidcarrier, in some examples, less than 1 wt % liquid carrier, in someexamples, less than 0.5 wt % liquid carrier. In some examples, the inkprinted on the print substrate is free from liquid carrier.

Thermoplastic Resin

The electrostatic ink composition comprising the release additive (whichmay be a transparent electrostatic ink composition) and/or the colouredelectrostatic ink composition may include a thermoplastic resin,referred to as the resin. A thermoplastic polymer is sometimes referredto as a thermoplastic resin. The resin for the electrostatic inkcomposition comprising the release additive (which may be a transparentelectrostatic ink composition) and the resin for the colouredelectrostatic ink composition may be the same as one another ordifferent from one another.

The resin typically includes a polymer. The resin can include, but isnot limited to, a thermoplastic polymer. In some examples, the polymerof the resin may be selected from ethylene acrylic acid copolymers;ethylene methacrylic acid copolymers; ethylene vinyl acetate copolymers;copolymers of ethylene (e.g., 80 wt % to 99.9 wt %), and alkyl (e.g., C1to C5) ester of methacrylic or acrylic acid (e.g., 0.1 wt % to 20 wt %);copolymers of ethylene (e.g., 80 wt % to 99.9 wt %), acrylic ormethacrylic acid (e.g., 0.1 wt % to 20.0 wt %) and alkyl (e.g., C1 toC5) ester of methacrylic or acrylic acid (e.g., 0.1 wt % to 20 wt %);polyethylene; polystyrene; isotactic polypropylene (crystalline);ethylene ethyl acrylate; polyesters; polyvinyl toluene; polyamides;styrene/butadiene copolymers; epoxy resins; acrylic resins (e.g.,copolymer of acrylic or methacrylic acid and at least one alkyl ester ofacrylic or methacrylic acid wherein alkyl is, in some examples, from 1to about 20 carbon atoms, such as methyl methacrylate (e.g., 50 wt % to90 wt %)/methacrylic acid (e.g., 0 wt % to 20 wt %)/ethylhexylacrylate(e.g., 10 wt % to 50 wt %)); ethylene-acrylate terpolymers:ethylene-acrylic esters-maleic anhydride (MAH) or glycidyl methacrylate(GMA) terpolymers; ethylene-acrylic acid ionomers and combinationsthereof.

The resin may comprise a polymer having acidic side groups. The polymerhaving acidic side groups may have an acidity of 50 mg KOH/g or more, insome examples, an acidity of 60 mg KOH/g or more, in some examples, anacidity of 70 mg KOH/g or more, in some examples, an acidity of 80 mgKOH/g or more, in some examples, an acidity of 90 mg KOH/g or more, insome examples, an acidity of 100 mg KOH/g or more, in some examples, anacidity of 105 mg KOH/g or more, in some examples, 110 mg KOH/g or more,in some examples, 115 mg KOH/g or more. The polymer having acidic sidegroups may have an acidity of 200 mg KOH/g or less, in some examples,190 mg or less, in some examples, 180 mg or less, in some examples, 130mg KOH/g or less, in some examples, 120 mg KOH/g or less. Acidity of apolymer, as measured in mg KOH/g can be measured by using standardprocedures known in the art, for example, using the procedure describedin ASTM D1386.

The resin may comprise a polymer, in some examples, a polymer havingacidic side groups, that has a melt flow rate of less than about 60 g/10minutes, in some examples, about 50 g/10 minutes or less, in someexamples, about 40 g/10 minutes or less, in some examples, 30 g/10minutes or less, in some examples, 20 g/10 minutes or less, in someexamples, 10 g/10 minutes or less. In some examples, all polymers havingacidic side groups and/or ester groups in the particles eachindividually have a melt flow rate of 90 g/10 minutes or less, in someexamples, 80 g/10 minutes or less, in some examples, 80 g/10 minutes orless, in some examples, 70 g/10 minutes or less, in some examples, 70g/10 minutes or less, in some examples, 60 g/10 minutes or less.

The polymer having acidic side groups can have a melt flow rate of about10 g/10 minutes to about 120 g/10 minutes, in some examples, about 10g/10 minutes to about 70 g/10 minutes, in some examples, about 10 g/10minutes to 40 g/10 minutes, in some examples, 20 g/10 minutes to 30 g/10minutes. The polymer having acidic side groups can have a melt flow rateof, in some examples, about 50 g/10 minutes to about 120 g/10 minutes,in some examples, 60 g/10 minutes to about 100 g/10 minutes. The meltflow rate can be measured by using standard procedures known in the art,for example, as described in ASTM D1238.

The acidic side groups may be in free acid form or may be in the form ofan anion and associated with at least one counterion, typically metalcounterions, for example, a metal selected from the alkali metals, suchas lithium, sodium and potassium, alkali earth metals, such as magnesiumor calcium, and transition metals, such as zinc. The polymer havingacidic side groups can be selected from resins such as copolymers ofethylene and an ethylenically unsaturated acid of either acrylic acid ormethacrylic acid; and ionomers thereof, such as methacrylic acid andethylene-acrylic or methacrylic acid copolymers which are at leastpartially neutralized with metal ions (e.g., Zn, Na, Li) such as SURLYN®ionomers. The polymer comprising acidic side groups can be a copolymerof ethylene and an ethylenically unsaturated acid of either acrylic ormethacrylic acid, where the ethylenically unsaturated acid of eitheracrylic or methacrylic acid constitutes from 5 wt % to about 25 wt % ofthe copolymer, in some examples, from 10 wt % to about 20 wt % of thecopolymer.

The resin may comprise two different polymers having acidic side groups.The two polymers having acidic side groups may have different acidities,which may fall within the ranges mentioned above. The resin may comprisea first polymer having acidic side groups that has an acidity of from 50mg KOH/g to 110 mg KOH/g and a second polymer having acidic side groupsthat has an acidity of 110 mg KOH/g to 130 mg KOH/g.

The resin may comprise two different polymers having acidic side groups:a first polymer having acidic side groups that has a melt flow rate ofabout 10 g/10 minutes to about 50 g/10 minutes and an acidity of from 50mg KOH/g to 110 mg KOH/g, and a second polymer having acidic side groupsthat has a melt flow rate of about 50 g/10 minutes to about 120 g/10minutes and an acidity of 110 mg KOH/g to 130 mg KOH/g. The first andsecond polymers may be absent of ester groups.

The resin may comprise two different polymers having acidic side groups:a first polymer that is a copolymer of ethylene (e.g., 92 to 85 wt %, insome examples, about 89 wt %) and acrylic or methacrylic acid (e.g., 8to 15 wt %, in some examples, about 11 wt %) having a melt flow rate of80 to 110 g/10 minutes and a second polymer that is a co-polymer ofethylene (e.g., about 80 to 92 wt %, in some examples, about 85 wt %)and acrylic acid (e.g., about 18 to 12 wt %, in some examples, about 15wt %) having a melt viscosity lower than that of the first polymer, thesecond polymer, for example, having a melt viscosity of 15000 poise orless, in some examples, a melt viscosity of 10000 poise or less, in someexamples, 1000 poise or less, in some examples, 100 poise or less, insome examples, 50 poise or less, in some examples, 10 poise or less.Melt viscosity can be measured by using standard techniques. The meltviscosity can be measured by using a rheometer, for example, acommercially available AR-2000 Rheometer from Thermal AnalysisInstruments, by using the geometry of: 25 mm steel plate-standard steelparallel plate, and finding the plate over plate rheometry isotherm at120° C., 0.01 Hz shear rate.

In any of the resins mentioned above, the ratio of the first polymerhaving acidic side groups to the second polymer having acidic sidegroups can be from about 10:1 to about 2:1. In another example, theratio can be from about 6:1 to about 3:1, in some examples, about 4:1.

The resin may comprise a polymer having a melt viscosity of 15000 poiseor less, in some examples, a melt viscosity of 10000 poise or less, insome examples, 1000 poise or less, in some examples, 100 poise or less,in some examples, 50 poise or less, in some examples, 10 poise or less;said polymer may be a polymer having acidic side groups as describedherein. The resin may comprise a first polymer having a melt viscosityof 15000 poise or more, in some examples, 20000 poise or more, in someexamples, 50000 poise or more, in some examples, 70000 poise or more;and in some examples, the resin may comprise a second polymer having amelt viscosity less than the first polymer, in some examples, a meltviscosity of 15000 poise or less, in some examples, a melt viscosity of10000 poise or less, in some examples, 1000 poise or less, in someexamples, 100 poise or less, in some examples, 50 poise or less, in someexamples, 10 poise or less. The resin may comprise a first polymerhaving a melt viscosity of 60000 poise or more, in some examples, from60000 poise to 100000 poise, in some examples, from 65000 poise to 85000poise; a second polymer having a melt viscosity of from 15000 poise to40000 poise, in some examples, 20000 poise to 30000 poise, and a thirdpolymer having a melt viscosity of 15000 poise or less, in someexamples, a melt viscosity of 10000 poise or less, in some examples,1000 poise or less, in some examples, 100 poise or less, in someexamples, 50 poise or less, in some examples, 10 poise or less; anexample of the first polymer is Nucrel 960 (from DuPont), and example ofthe second polymer is Nucrel 699 (from DuPont), and an example of thethird polymer is AC-5120 (from Honeywell). The first, second and thirdpolymers may be polymers having acidic side groups as described herein.The melt viscosity can be measured using a rheometer, for example, acommercially available AR-2000 Rheometer from Thermal AnalysisInstruments, using the geometry of: 25 mm steel plate-standard steelparallel plate, and finding the plate over plate rheometry isotherm at120° C., 0.01 Hz shear rate.

If the resin comprises a single type of resin polymer, the resin polymer(excluding any other components of the electrostatic ink composition)may have a melt viscosity of 6000 poise or more, in some examples, amelt viscosity of 8000 poise or more, in some examples, a melt viscosityof 10000 poise or more, in some examples, a melt viscosity of 12000poise or more. If the resin comprises a plurality of polymers all thepolymers of the resin may together form a mixture (excluding any othercomponents of the electrostatic ink composition) that has a meltviscosity of 6000 poise or more, in some examples, a melt viscosity of8000 poise or more, in some examples, a melt viscosity of 10000 poise ormore, in some examples, a melt viscosity of 12000 poise or more. Meltviscosity can be measured by using standard techniques. The meltviscosity can be measured by using a rheometer, for example, acommercially available AR-2000 Rheometer from Thermal AnalysisInstruments, using the geometry of: 25 mm steel plate-standard steelparallel plate, and finding the plate over plate rheometry isotherm at120° C., 0.01 Hz shear rate.

The resin may comprise two different polymers having acidic side groupsthat are selected from copolymers of ethylene and an ethylenicallyunsaturated acid of either methacrylic acid or acrylic acid; andionomers thereof, such as methacrylic acid and ethylene-acrylic ormethacrylic acid copolymers which are at least partially neutralizedwith metal ions (e.g., Zn, Na, Li) such as SURLYN® ionomers. The resinmay comprise (i) a first polymer that is a copolymer of ethylene and anethylenically unsaturated acid of either acrylic acid or methacrylicacid, wherein the ethylenically unsaturated acid of either acrylic ormethacrylic acid constitutes from 8 wt % to about 16 wt % of thecopolymer, in some examples, 10 wt % to 16 wt % of the copolymer; and(ii) a second polymer that is a copolymer of ethylene and anethylenically unsaturated acid of either acrylic acid and methacrylicacid, wherein the ethylenically unsaturated acid of either acrylic ormethacrylic acid constitutes from 12 wt % to about 30 wt % of thecopolymer, in some examples, from 14 wt % to about 20 wt % of thecopolymer, in some examples, from 16 wt % to about 20 wt % of thecopolymer, in some examples, from 17 wt % to 19 wt % of the copolymer.

In an example, the thermoplastic resin constitutes about 10 to 99%, insome examples, about 15 to 95%, by weight of the solids of theelectrostatic ink composition comprising the release additive (which maybe a transparent electrostatic ink composition) and/or the colouredelectrostatic ink composition. In another example, the resin constitutesabout 20 to 95% by weight of the solids of the electrostatic inkcomposition comprising the release additive (which may be a transparentelectrostatic ink composition) transparent and/or the colouredelectrostatic ink composition. In another example, the resin constitutesabout 25 to 95% by weight of the solids of the electrostatic inkcomposition comprising the release additive (which may be a transparentelectrostatic ink composition) and/or the coloured electrostatic inkcomposition. In another example, the resin constitutes about 35 to 95%by weight, in some examples, from 75 to 95% by weight, of the solids ofthe electrostatic ink composition comprising the release additive (whichmay be a transparent electrostatic ink composition) and/or the colouredelectrostatic ink composition. In another example, the resin constitutesabout 35 to 95% by weight, in some examples, from 75 to 99% by weight ofthe solids of the electrostatic ink composition comprising the releaseadditive (which may be a transparent electrostatic ink composition)and/or the coloured electrostatic ink composition.

The thermoplastic resin may comprise a polymer having acidic sidegroups, as described above (which may be free of ester side groups), anda polymer having ester side groups. The polymer having ester side groupsis, in some examples, a thermoplastic polymer. The polymer having esterside groups may further comprise acidic side groups. The polymer havingester side groups may be a co-polymer of a monomer having ester sidegroups and a monomer having acidic side groups. The polymer may be aco-polymer of a monomer having ester side groups, a monomer havingacidic side groups, and a monomer absent of any acidic and ester sidegroups. The monomer having ester side groups may be a monomer selectedfrom esterified acrylic acid or esterified methacrylic acid. The monomerhaving acidic side groups may be a monomer selected from acrylic ormethacrylic acid. The monomer absent of any acidic and ester side groupsmay be an alkylene monomer, including, but not limited to, ethylene orpropylene. The esterified acrylic acid or esterified methacrylic acidmay, respectively, be an alkyl ester of acrylic acid or an alkyl esterof methacrylic acid. The alkyl group in the alkyl ester of acrylic ormethacrylic acid may be an alkyl group having 1 to 30 carbon atoms, insome examples, 1 to 20 carbon atoms, in some examples, 1 to 10 carbonatoms; in some examples, selected from methyl, ethyl, iso-propyl,n-propyl, t-butyl, iso-butyl, n-butyl and pentyl.

The polymer having ester side groups may be a co-polymer of a firstmonomer having ester side groups, a second monomer having acidic sidegroups and a third monomer which is an alkylene monomer absent of anyacidic and ester side groups. The polymer having ester side groups maybe a co-polymer of (i) a first monomer having ester side groups selectedfrom esterified acrylic acid or esterified methacrylic acid, in someexamples, an alkyl ester of acrylic or methacrylic acid, (ii) a secondmonomer having acidic side groups selected from acrylic or methacrylicacid and (iii) a third monomer which is an alkylene monomer selectedfrom ethylene and propylene. The first monomer may constitute 1 to 50%by weight of the co-polymer, in some examples, 5 to 40% by weight, insome examples, 5 to 20% by weight of the copolymer, in some examples, 5to 15% by weight of the copolymer. The second monomer may constitute 1to 50% by weight of the co-polymer, in some examples, 5 to 40% by weightof the co-polymer, in some examples, 5 to 20% by weight of theco-polymer, in some examples, 5 to 15% by weight of the copolymer. In anexample, the first monomer constitutes 5 to 40% by weight of theco-polymer, the second monomer constitutes 5 to 40% by weight of theco-polymer, and with the third monomer constituting the remaining weightof the copolymer. In an example, the first monomer constitutes 5 to 15%by weight of the co-polymer, the second monomer constitutes 5 to 15% byweight of the co-polymer, with the third monomer constituting theremaining weight of the copolymer. In an example, the first monomerconstitutes 8 to 12% by weight of the co-polymer, the second monomerconstitutes 8 to 12% by weight of the co-polymer, with the third monomerconstituting the remaining weight of the copolymer. In an example, thefirst monomer constitutes about 10% by weight of the co-polymer, thesecond monomer constitutes about 10% by weight of the co-polymer, andwith the third monomer constituting the remaining weight of thecopolymer. The polymer having ester side groups may be selected from theBynel® class of monomer, including Bynel 2022 and Bynel 2002, which areavailable from DuPont®.

The polymer having ester side groups may constitute 1% or more by weightof the total amount of the resin polymers in the resin, for example, thetotal amount of the polymer or polymers having acidic side groups andpolymer having ester side groups. The polymer having ester side groupsmay constitute 5% or more by weight of the total amount of the resinpolymers in the resin, in some examples, 8% or more by weight of thetotal amount of the resin polymers in the resin, in some examples, 10%or more by weight of the total amount of the resin polymers in theresin, in some examples, 15% or more by weight of the total amount ofthe resin polymers in the resin, in some examples, 20% or more by weightof the total amount of the resin polymers in the resin, in someexamples, 25% or more by weight of the total amount of the resinpolymers in the resin, in some examples, 30% or more by weight of thetotal amount of the resin polymers in the resin, in some examples, 35%or more by weight of the total amount of the resin polymers in theresin. The polymer having ester side groups may constitute from 5 to 50%by weight of the total amount of the resin polymers in the resin, insome examples 10 to 40% by weight of the total amount of the resinpolymers in the resin, in some examples 15 to 30% by weight of the totalamount of the polymers in the resin.

The polymer having ester side groups may have an acidity of 50 mg KOH/gor more, in some examples, an acidity of 60 mg KOH/g or more, in someexamples, an acidity of 70 mg KOH/g or more, in some examples, anacidity of 80 mg KOH/g or more. The polymer having ester side groups mayhave an acidity of 100 mg KOH/g or less, in some examples, 90 mg KOH/gor less. The polymer having ester side groups may have an acidity of 60mg KOH/g to 90 mg KOH/g, in some examples, 70 mg KOH/g to 80 mg KOH/g.

The polymer having ester side groups may have a melt flow rate of about10 g/10 minutes to about 120 g/10 minutes, in some examples, about 10g/10 minutes to about 50 g/10 minutes, in some examples, about 20 g/10minutes to about 40 g/10 minutes, in some examples, about 25 g/10minutes to about 35 g/10 minutes.

In an example, the polymer or polymers of the resin can be selected fromthe Nucrel family of toners (e.g., Nucrel 403™, Nucrel 407™, Nucrel609HS™, Nucrel 908HS™ Nucrel 1202HC™, Nucrel 30707™, Nucrel 1214™,Nucrel 903™, Nucrel 3990™, Nucrel 910™, Nucrel 925™, Nucrel 699™, Nucrel599™, Nucrel 960™, Nucrel RX 76™, Nucrel 2806™, Bynell 2002, Bynell2014, and Bynell 2020 (sold by E. I. du PONT)), the Aclyn family oftoners (e.g., Aclyn 201, Aclyn 246, Aclyn 285, and Aclyn 295), and theLotader family of toners (e.g., Lotader 2210, Lotader, 3430, and Lotader8200 (sold by Arkema)).

Charge Director and Charge Adjuvant

In some examples, the electrostatic ink composition comprising therelease additive (which may be a transparent electrostatic inkcomposition) and/or the coloured electrostatic ink composition includeseither a charge director or a charge adjuvant or both.

The charge director may be added in order to impart and/or maintainsufficient electrostatic charge on ink particles during electrostaticprinting, which may be particles comprising the thermoplastic resin andthe release additive (for the electrostatic ink composition comprisingthe release additive, which may be a transparent electrostatic inkcomposition), or the colorant (for the coloured electrostatic inkcomposition). The charge director may comprise ionic compounds,particularly metal salts of fatty acids, metal salts ofsulfo-succinates, metal salts of oxyphosphates, metal salts ofalkyl-benzenesulfonic acid, metal salts of aromatic carboxylic acids orsulfonic acids, as well as zwitterionic and non-ionic compounds, such aspolyoxyethylated alkylamines, lecithin, polyvinylpyrrolidone, organicacid esters of polyvalent alcohols, and so forth. The charge directorcan be selected from, but is not limited to, oil-soluble petroleumsulfonates (e.g., neutral Calcium Petronate™, neutral Barium Petronate™,and basic Barium Petronate™), polybutylene succinimides (e.g., OLOA™1200 and Amoco 575), and glyceride salts (e.g., sodium salts ofphosphated mono- and diglycerides with unsaturated and saturated acidsubstituents), sulfonic acid salts including, but not limited to,barium, sodium, calcium, and aluminium salts of sulfonic acid. Thesulfonic acids may include, but are not limited to, alkyl sulfonicacids, aryl sulfonic acids, and sulfonic acids of alkyl succinates. Thecharge director can impart a negative charge or a positive charge on theresin-containing particles of an electrostatic ink composition.

In some examples, the electrostatic ink composition comprising therelease additive (which may be a transparent electrostatic inkcomposition) and/or the coloured electrostatic ink composition comprisesa charge director comprising a simple salt. Simple salts are salts thatdo not form micelles by themselves, although they may form a core formicelles with a micelle forming salt. The ions constructing the simplesalts are all hydrophilic. The simple salt may include a cation selectedfrom the group consisting of Mg, Ca, Ba, NH₄, tert-butyl ammonium, Li⁺,and Al³⁺, or from any sub-group thereof. The simple salt may include ananion selected from the group consisting of SO₄ ²⁻, PO³⁻, NO³⁻, HPO₄ ²⁻,CO₃ ²⁻, acetate, trifluoroacetate (TFA), Cl⁻, BF₄ ⁻, F⁻, ClO₄ ⁻, andTiO₃ ⁴⁻, or from any sub-group thereof. The simple salt may be selectedfrom CaCO₃, Ba₂TiO₃, Al₂(SO₄), Al(NO₃)₃, Ca₃(PO₄)₂, BaSO₄, BaHPO₄,Ba₂(PO₄)₃, CaSO₄, (NH₄)₂CO₃, (NH₄)₂SO₄, NH₄OAc, tert-butyl ammoniumbromide, NH₄NO₃, LiTFA, Al₂(SO₄)₃, LiClO₄ and LiBF₄, or any sub-groupthereof.

The charge director may include at least one of (i) soya lecithin, (ii)a barium sulfonate salt, such as basic barium petronate (BPP), and (iii)an isopropyl amine sulfonate salt. Basic barium petronate is a bariumsulfonate salt of a 21-26 hydrocarbon alkyl, and can be obtained, forexample, from Chemtura. An example isopropyl amine sulfonate salt isdodecyl benzene sulfonic acid isopropyl amine, which is available fromCroda.

In some examples, the electrostatic ink composition comprising therelease additive (which may be a transparent electrostatic inkcomposition) and/or the coloured electrostatic ink composition comprisesa charge director comprising a sulfosuccinate salt of the generalformula MA_(n), wherein M is a metal, n is the valence of M, and A is anion of the general formula (I):

[R¹—O—C(O)CH₂CH(SO₃)C(O)—O—R²]⁻  (I)

wherein each of R¹ and R² is an alkyl group.

The sulfosuccinate salt of the general formula MA_(n) is an example of amicelle forming salt. The charge director may be substantially free ofor free of an acid of the general formula HA, where A is as describedabove. The charge director may include micelles of said sulfosuccinatesalt enclosing at least some of the nanoparticles. The charge directormay include at least some nanoparticles having a size of 200 nm or less,and/or in some examples 2 nm or more.

In the formula [R₁—O—C(O)CH₂CH(SO₃ ⁻)C(O)—O—R₂], in some examples, eachof R¹ and R² is an aliphatic alkyl group. In some examples, each of R¹and R² independently is a C6-25 alkyl. In some examples, said aliphaticalkyl group is linear. In some examples, said aliphatic alkyl group isbranched. In some examples, said aliphatic alkyl group includes a linearchain of more than 6 carbon atoms. In some examples, R¹ and R² are thesame. In some examples, at least one of R¹ and R² is C₁₃H₂₇. In someexamples, M is Na, K, Cs, Ca, or Ba.

In some examples, the charge director constitutes about 0.001 to 20% byweight, in some examples, 0.01 to 20% by weight, in some examples, 0.01to 10% by weight, in some examples, 0.01 to 1% by weight of the solidsof the electrostatic ink composition comprising the release additive(which may be a transparent electrostatic ink composition) and/or thecoloured electrostatic ink composition. In some examples, the chargedirector constitutes about 0.001 to 0.15% by weight of the solids of theelectrostatic ink composition comprising the release additive (which maybe a transparent electrostatic ink composition) and/or the colouredelectrostatic ink composition, in some examples, 0.001 to 0.15%, in someexamples, 0.001 to 0.02% by weight of the solids of the electrostaticink composition comprising the release additive (which may be atransparent electrostatic ink composition) and/or the colouredelectrostatic ink composition, in some examples, 0.1 to 2% by weight ofthe solids of the electrostatic ink composition comprising the releaseadditive (which may be a transparent electrostatic ink composition)and/or the coloured electrostatic ink composition, in some examples, 0.2to 1.5% by weight of the solids of the electrostatic ink compositioncomprising the release additive (which may be a transparentelectrostatic ink composition) and/or the coloured electrostatic inkcomposition, in some examples, 0.1 to 1% by weight of the solids of theelectrostatic ink composition comprising the release additive (which maybe a transparent electrostatic ink composition) and/or the colouredelectrostatic ink composition, in some examples, 0.2 to 0.8% by weightof the solids of the electrostatic ink composition comprising therelease additive (which may be a transparent electrostatic inkcomposition) and/or the coloured electrostatic ink composition. In someexamples, the charge director is present in an amount of at least 1 mgof charge director per gram of solids of the electrostatic inkcomposition comprising the release additive (which may be a transparentelectrostatic ink composition) and/or the coloured electrostatic inkcomposition (which will be abbreviated to mg/g), in some examples, atleast 2 mg/g, in some examples, at least 3 mg/g, in some examples, atleast 4 mg/g, in some examples, at least 5 mg/g. In some examples, thecharge director is present in the amounts stated above, and the chargedirector is present in an amount of from 1 mg to 50 mg of chargedirector per gram of solids of the electrostatic ink compositioncomprising the release additive (which may be a transparentelectrostatic ink composition) and/or the coloured electrostatic inkcomposition (which will be abbreviated to mg/g), in some examples, from1 mg/g to 25 mg/g, in some examples, from 1 mg/g to 20 mg/g, in someexamples, from 1 mg/g to 15 mg/g, in some examples, from 1 mg/g to 10mg/g, in some examples, from 3 mg/g to 20 mg/g, in some examples, from 3mg/g to 15 mg/g, in some examples, from 5 mg/g to 10 mg/g.

A charge adjuvant may promote charging of the particles when a chargedirector is present in the electrostatic ink composition comprising therelease additive (which may be a transparent electrostatic inkcomposition) and/or the coloured electrostatic ink composition duringprinting. The charge adjuvant can include, but is not limited to, bariumpetronate, calcium petronate, Co salts of naphthenic acid, Ca salts ofnaphthenic acid, Cu salts of naphthenic acid, Mn salts of naphthenicacid, Ni salts of naphthenic acid, Zn salts of naphthenic acid, Fe saltsof naphthenic acid, Ba salts of stearic acid, Co salts of stearic acid,Pb salts of stearic acid, Zn salts of stearic acid, Al salts of stearicacid, Zn salts of stearic acid, Cu salts of stearic acid, Pb salts ofstearic acid, Fe salts of stearic acid, metal carboxylates (e.g., Altristearate, Al octanoate, Li heptanoate, Fe stearate, Fe distearate, Bastearate, Cr stearate, Mg octanoate, Ca stearate, Fe naphthenate, Znnaphthenate, Mn heptanoate, Zn heptanoate, Ba octanoate, Al octanoate,Co octanoate, Mn octanoate, and Zn octanoate), Co lineolates, Mnlineolates, Pb lineolates, Zn lineolates, Ca oleates, Co oleates, Znpalmirate, Ca resinates, Co resinates, Mn resinates, Pb resinates, Znresinates, AB diblock copolymers of 2-ethylhexylmethacrylate-co-methacrylic acid calcium and ammonium salts, copolymersof an alkyl acrylamidoglycolate alkyl ether (e.g., methylacrylamidoglycolate methyl ether-co-vinyl acetate), and hydroxybis(3,5-di-tert-butyl salicylic) aluminate monohydrate. In an example,the charge adjuvant is or includes aluminum di- or tristearate. Thecharge adjuvant may be present in an amount of about 0.1 to 5% byweight, in some examples, about 0.1 to 1% by weight, in some examples,about 0.3 to 0.8% by weight of the solids of the electrostatic inkcomposition comprising the release additive (which may be a transparentelectrostatic ink composition) and/or the coloured electrostatic inkcomposition, in some examples, about 1 to 3% by weight of the solids ofthe electrostatic ink composition comprising the release additive (whichmay be a transparent electrostatic ink composition) and/or the colouredelectrostatic ink composition, in some examples, about 1.5 to 2.5% byweight of the solids of the electrostatic ink composition comprising therelease additive (which may be a transparent electrostatic inkcomposition) and/or the coloured electrostatic ink composition.

In some examples, the electrostatic ink composition comprising therelease additive (which may be a transparent electrostatic inkcomposition) and/or the coloured electrostatic ink composition furtherincludes, for example, as a charge adjuvant, a salt of a multivalentcation and a fatty acid anion. The salt of a multivalent cation and afatty acid anion can act as a charge adjuvant. The multivalent cationmay, in some examples, be a divalent or a trivalent cation. In someexamples, the multivalent cation is selected from Group 2, transitionmetals, Group 3 and Group 4 in the Periodic Table. In some examples, themultivalent cation includes a metal selected from Ca, Sc, Ti, V, Cr, Mn,Fe, Co, Ni, Cu, Zn, Al and Pb. In some examples, the multivalent cationis Al³⁺. The fatty acid anion may be selected from a saturated orunsaturated fatty acid anion. The fatty acid anion may be selected froma C₈ to C₂₆ fatty acid anion, in some examples, a C₁₄ to C₂₂ fatty acidanion, in some examples, a C₁₆to C₂₀ fatty acid anion, in some examples,a C₁₇, C₁₈ or C₁₉ fatty acid anion. In some examples, the fatty acidanion is selected from a caprylic acid anion, capric acid anion, lauricacid anion, myristic acid anion, palmitic acid anion, stearic acidanion, arachidic acid anion, behenic acid anion and cerotic acid anion.

The charge adjuvant, which may, for example, be or include a salt ofmultivalent cation and a fatty acid anion, may be present in an amountof 0.1 wt % to 5 wt % of the solids of the electrostatic ink compositioncomprising the release additive (which may be a transparentelectrostatic ink composition) and/or the coloured electrostatic inkcomposition, in some examples, in an amount of 0.1 wt % to 2 wt % of thesolids of the electrostatic ink composition comprising the releaseadditive (which may be a transparent electrostatic ink composition)and/or the coloured electrostatic ink composition, in some examples, inan amount of 0.1 wt % to 2 wt % of the solids of the electrostatic inkcomposition comprising the release additive (which may be a transparentelectrostatic ink composition) and/or the coloured electrostatic inkcomposition, in some examples, in an amount of 0.3 wt % to 1.5 wt % ofthe solids of the electrostatic ink composition comprising the releaseadditive (which may be a transparent electrostatic ink composition)and/or the coloured electrostatic ink composition, in some examples,about 0.5 wt % to 1.2 wt % of the solids of the electrostatic inkcomposition comprising the release additive (which may be a transparentelectrostatic ink composition) and/or the coloured electrostatic inkcomposition, in some examples, about 0.8 wt % to 1 wt % of the solids ofthe electrostatic ink composition comprising the release additive (whichmay be a transparent electrostatic ink composition) and/or the colouredelectrostatic ink composition, in some examples, about 1 wt % to 3 wt %of the solids of the electrostatic ink composition comprising therelease additive (which may be a transparent electrostatic inkcomposition) and/or the coloured electrostatic ink composition, in someexamples, about 1.5 wt % to 2.5 wt % of the solids of the electrostaticink composition comprising the release additive (which may be atransparent electrostatic ink composition) and/or the colouredelectrostatic ink composition.

Other Additives

The electrostatic ink composition comprising the release additive (whichmay be a transparent electrostatic ink composition) and/or the colouredelectrostatic ink composition may include an additive or a plurality ofadditives. The additive or plurality of additives may be added at anystage of the method. The additive or plurality of additives may beselected from a wax, a surfactant, biocides, organic solvents, viscositymodifiers, materials for pH adjustment, sequestering agents,preservatives, compatibility additives, emulsifiers and the like. Thewax may be an incompatible wax. As used herein, “incompatible wax” mayrefer to a wax that is incompatible with the resin. Specifically, thewax phase separates from the resin phase upon the cooling of the resinfused mixture on a print substrate during and after the transfer of theink film to the print substrate, for example, from an intermediatetransfer member, which may be a heated blanket.

Substrate Having a First Layer Showing Information Thereon

The substrate having a first layer may be or comprise any suitablematerial for supporting the second to fourth layers. The first layermay, for example, be or comprise any suitable material capable of havinginformation displayed, for example, printed, thereon. The first layermay comprise a material selected from an organic or inorganic material.The first layer may comprise a natural polymeric material, for example,cellulose. The first layer may comprise a synthetic polymeric material,for example, a plastic. The first layer may comprise a polymer formedfrom alkylene monomers, including, but not limited to, polyethylene andpolypropylene, and copolymers such as styrene-polybutadiene. Thepolypropylene may be biaxially orientated polypropylene. The materialmay comprise a metal, which may be in sheet form. The metal may beselected from or made from, for instance, aluminum (Al), silver (Ag),tin (Sn), copper (Cu), or mixtures thereof. In some examples, thesubstrate comprises a cellulosic paper, card or cardboard. In someexamples, the cellulosic paper is coated with a polymeric material, forexample, a polymer formed from styrene-butadiene resin. In someexamples, the cellulosic paper has an inorganic material bound to itssurface (before printing with ink) with a polymeric material, whereinthe inorganic material may be selected from, for example, kaolinite orcalcium carbonate. The substrate may be a cellulosic print substrate,such as paper. The cellulosic substrate may be a coated cellulosic printsubstrate, for example, having a coating of a polymeric materialthereon.

The information on the first layer may comprise any indicia, forexample, indicia selected from pictures, words, symbols, characters,letters and/or numbers. The pictures, words, symbols, characters,letters and/or numbers may be from any language, alphabet or numberingsystem. In a collection of scratch-off structures, the informationunderlying the second, third and fourth layers may vary, that is, suchthat different scratch-off structures display different information thatcan be revealed when the third and fourth layer are scratched off. Thefirst layer may also comprise other information, in locations other thanunder the third and fourth layers, and this information may be the samein the collection of scratch-off structures.

The information may be printed on the first layer, and may be printed byany suitable print method, including, but not limited to electrostaticprinting, ink-jet printing and offset lithography. The information maybe printed and comprise a colourant selected from cyan, magenta, yellow,black and white. The information on the first layer may be printed usingthe electrostatic printing of a coloured electrostatic ink, which may beas described herein for the fourth layer.

In some examples, an electrostatic ink comprising a component selectedfrom a fatty acid ester having a plurality of hydroxyl substituents anda fatty acid amide having a plurality of hydroxyl substituents isprinted on the first layer, and in some examples, one or more furtherlayers are disposed between the printed electrostatic ink and the firstlayer. The electrostatic ink comprising a component selected from afatty acid ester having a plurality of hydroxyl substituents and a fattyacid amide having a plurality of hydroxyl substituents may be a colouredink, e.g. containing one or more pigments, or a transparentelectrostatic ink, e.g. lacking or substantially lacking a pigment.

Second Layer

A second layer may overlie the first layer. The second layer maycomprise a polymeric film and/or be substantially transparent.“Substantially transparent” in the present context indicates that theinformation on the first layer is visible through the second layer.“Visible through the second layer” may indicate that it can be seen by ahuman from 30 cm, the human having a visual acuity of 1.0, as measuredin accordance with ISO 8596.

The second layer typically acts as a protective layer over theinformation on the first layer, such that on scratching the third andfourth layers off, the second layer remains in place. The second layermay have a higher abrasion resistance, for example, as tested by using asuitable test, such as ASTM D5181-09, than the third and/or fourthlayer.

The polymeric film of the second layer may, for example, have beenformed from or be an overprint varnish or primer. Such overprintvarnishes are typically applied as protective layers over printedsurfaces. An overprint varnish may be applied in liquid form, then curedand/or hardened, with solvent evaporation as appropriate to leave thesolid overprint varnish. The overprint varnish may be selected from aUV-curable varnish, an aqueous-based varnish, and a solvent-basedvarnish. The solvent-based varnish may comprise a vinyl acetate-basedresin, an acrylic-based resin, a polyvinyl butyral (PVB)-based resin ora wax-based resin, such as oil-based alkyd resins. The water-basedvarnish may comprise a resin based on a styrenic binding system and/oran acrylic binding system. In some examples, the water-based varnishcomprises a vinyl acrylic resin, such as a polyacrylic acid copolymer,such as an ethylene acrylic acid copolymer. The UV-curable varnish maycontain polymers and/or monomers that cure, for example, furtherpolymerise and/or cross-link, when exposed to UV radiation.

The second layer may comprise a polymeric film adhered to the firstlayer. In some examples, the polymeric film is substantiallytransparent.

In some examples, the polymeric film may be or comprises a sheet ofplastic. The sheet of plastic may be a continuous sheet. The sheet ofplastic may be a non-porous sheet of plastic.

The polymeric film may be or comprise a monoaxially stretched orbiaxially stretched plastic. In some examples, the polymeric film maycomprise a single layer of material, which may comprise or be plastic,or a plurality of layers of material, each of which may comprise or beplastic, and may be different to one another.

In some examples, the polymeric film is in the form of a sheet, in someexamples, a sheet of plastic, having a thickness of at least 5 μm, insome examples, at least 10 μm, in some examples, at least 30 μm, in someexamples, at least 40 μm. In some examples, the polymeric film is in theform of a sheet having a thickness of from 5 μm to 1 mm, in someexamples, 5 μm to 200 μm, in some examples, 5 μm to 100 μm, in someexamples, 10 μm to 80 μm, in some examples, 10 μm to 60 μm, in someexamples, 10 μm to 30 μm, in some examples, 20 μm to 60 μm, in someexamples, 30 μm to 50 μm.

In some examples, the polymeric film comprises a plastic selected from apolyalkylene, polyethylene terephthalate, polyethylene terephthalateglycol, polystyrene, polyvinyl chloride, polyethylene-2,6-napthalate,polyhexamethylene adipamide, polymers of alpha mono-olefinicallyunsaturated hydrocarbons having polymer producing unsaturation such asbutene, vinyl acetate, methylacrylate, 2-ethyl hexyl acrylate, isoprene,butadiene acrylamide, ethylacrylate and N-methyl-n-vinyl acetamide. Insome examples, the polymeric film comprises a plastic selected frompolyethylene, polypropylene, polyisopropylethylene andpolyisobutylethylene.

In some examples, the polymeric film comprises a monoaxially orbiaxially oriented sheet of plastic. In some examples, the polymericfilm comprises a plastic selected from an oriented polypropylene and anoriented polyethylene. In some examples, the plastic of the polymericfilm is selected from monoaxially oriented polypropylene, biaxiallyoriented polypropylene, monoaxially oriented polyethylene and biaxiallyoriented polyethylene.

The polymeric film may be adhered to the first layer by an adhesive orby direct fusing of the materials of the first and second layers. In anexample, the adhesive is a thermally fusible adhesive. In an example,the adhesive is a hot-melt adhesive. In an example, the adhesive is apressure-sensitive adhesive. The adhesive may be selected from ethylenevinyl acetate (EVA), polyethylene, polystyrene, polypropylene,polybutene, polyester, poly(meth)acrylate, polyamides, thermoplasticpolyimides, polyesters, polyurethanes, styrene block co-polymers (suchas styrene-butadiene-styrene, styrene-isoprene-styrene,styrene-ethylene/butylene-styrene and styrene-ethylene/propylene).

In some examples, the polymeric film is present with a coat weight of atleast 0.1 grams per square meter (gsm), in some examples at least 0.3gsm, in some examples at least 0.5 gsm, in some examples at least 1.5gsm. In some examples, the polymeric film is present with a coat weightof 10 grams per square meter (gsm) or less, in some examples 7 gsm orless, in some examples 5 gsm or less, in some examples at least 3 gsm orless, in some examples at least 3 gsm or less. In some examples, thepolymeric film is present with a coat weight of at least 0.1 grams persquare meter (gsm) to 10 gsm, in some examples 0.3 gsm to 5 gsm, in someexamples 0.5 gsm to 3 gsm, in some examples 1 gsm to 2 gsm, in someexamples about 1.5 gsm.

Third Layer

In some examples, an electrostatic ink comprising a component selectedfrom a fatty acid ester having a plurality of hydroxyl substituents anda fatty acid amide having a plurality of hydroxyl substituents isprinted on the second layer. The electrostatic ink comprising acomponent selected from a fatty acid ester having a plurality ofhydroxyl substituents and a fatty acid amide having a plurality ofhydroxyl substituents may be a coloured ink, e.g. containing one or morepigments, or a transparent electrostatic ink, e.g. lacking orsubstantially lacking a pigment. A fourth layer may or may not bedisposed on the third layer.

The third layer may comprise an electrostatic ink comprising the releaseadditive, wherein the release additive selected from a fatty acid esterhaving a plurality of hydroxyl substituents and a fatty acid amidehaving a plurality of hydroxyl substituents. In some examples, theelectrostatic ink is a transparent electrostatic ink. “Transparent” inthe present context indicates that the information on the first layer isvisible through the second layer and the third layer. “Visible throughthe second layer and the third layer” may indicate that it can be seenby a human from 30 cm, the human having a visual acuity of 1.0, asmeasured in accordance with ISO 8596. In some examples, theelectrostatic ink is a liquid electrostatic ink.

In some examples, the third layer, once printed, may form a layer of 10μm or less in thickness, for example, 9 μm or less in thickness, 8 μm orless in thickness, 7 μm or less in thickness, 6 μm or less in thickness,5 μm or less in thickness, 4 μm or less in thickness, 3 μm or less inthickness, 2 μm or less in thickness, 1.5 μm or less in thickness. Insome examples, the transparent electrostatic ink composition is about 1μm in thickness.

In some examples, the third layer, once printed, the transparentelectrostatic ink composition forms a layer of 0.1 μm or greater inthickness, for example, 0.2 μm or greater in thickness, 0.3 μm orgreater in thickness, 0.4 μm or greater in thickness, 0.5 μm or greaterin thickness, 0.6 μm or greater in thickness, 0.7 μm or greater inthickness, 0.8 μm or greater in thickness, 0.9 μm or greater inthickness.

Fourth Layer

The fourth layer is a coloured layer. In some examples, the fourth layeracts to obscure the information on the first layer, but can be scratchedoff, typically with the third layer, to reveal the underlyinginformation on the first layer. The fourth layer may be a printed layer,and may be printed by any suitable print method, including, but notlimited to electrostatic printing, ink-jet printing and offsetlithography. The fourth layer may comprise a colourant which may beselected from cyan, magenta, yellow, black and white colourants.

In some examples, the fourth layer comprises a coloured electrostaticink, printed in an electrostatic printing process, which may be a dry ora liquid electrostatic printing process. The coloured electrostatic inkmay comprise a colourant selected from cyan, magenta, yellow, black andwhite. The coloured electrostatic ink may comprise colourant in at least5 wt % of the solids, in some examples, at least 8 wt % of the solids,in some examples, at least 10 wt % of the solids, in some examples, atleast 10 wt % of the solids. The coloured electrostatic ink, which mayalso be termed a coloured electrostatic ink composition, may comprise athermoplastic resin, which may be the same as or different from anythermoplastic resin that the transparent electrostatic ink contains.

The coloured electrostatic ink may substantially lack (e.g., containless than 1 wt % of the solids) or lack the release additive asdescribed herein, i.e. the component selected from a fatty acid esterhaving a plurality of hydroxyl substituents and a fatty acid amidehaving a plurality of hydroxyl substituents.

In some examples, some of the coloured material of the fourth layer maybe printed directly onto the second layer. In some examples, thecoloured material of the fourth layer extends beyond the third layer,such that it directly contacts the second layer.

In some examples, the coloured electrostatic ink composition comprises apigment and all components of the transparent electrostatic inkcomposition described above except the release additive.

Scratch-Off Structure

The present disclosure provides a scratch-off structure comprising, insome examples, the following layers in order:

-   -   a substrate having a first layer showing information thereon,    -   a second layer comprising a polymeric film and being        substantially transparent;    -   a third layer comprising a transparent electrostatic ink;    -   a fourth layer, wherein the fourth layer is coloured.

The scratch-off structure may have been produced by the method describedherein, and may comprise the components mentioned for each layer herein.

As indicated, FIG. 1 schematically depicts a cross-section of an exampleof a scratch-off structure before (a) and after (b) the third and fourthlayers have been scratched off.

FIGS. 2(a) to (c) shows schematically an example of a scratch-offstructure being produced and then having a portion scratched off toreveal information.

FIG. 1a shows a cross-sectional diagram of an example scratch-offstructure (100). The scratch-off structure comprises a substrate (101 a)having a first layer showing information (101 b) thereon. A second layercomprising a polymeric film (102) and being substantially transparent isdisposed on the substrate (101 a) having a first layer showinginformation (101 b) thereon. A transparent third layer (103) comprisinga transparent electrostatic ink having the release additive as describedherein is disposed on the second layer (102) over at least the areacovered by the information (101 b) shown on the substrate (101 a). Afourth, coloured, layer (104) is disposed on the third layer (103) andin some examples on any areas of the second layer (102) not covered bythe third layer (103). The fourth coloured layer obscures theinformation on the first layer.

FIG. 1b shows a cross-sectional diagram of the scratch-off structure(100) shown in FIG. 1a after the scratch-off portions (the third andfourth layers) have been scratched off. The adhesion of the third layer(103) to the second layer (102) is low enough that the third layer andany layers, such as the fourth layer (104), adhered to it can be removedby use of abrasion, such as scratching with a coin, finger nail, orother suitable object. The removal of the third (103) and fourth (104)layers allows the information (101 b) shown on the substrate (101 a) tobecome visible.

FIG. 2 shows schematically an example of a scratch-off structure, whenviewing from above the layers. FIG. 2a depicts an example of thesubstrate having a first layer showing information (in this case thephrase “You win: A car”). FIG. 2b depicts a scratch-off structure inwhich a third layer comprising a transparent electrostatic ink has beenprinted in a circular portion over part of the information (“a car”)shown on the substrate and over which has been printed an opaque circle,forming a part of the fourth, coloured, layer. The remaining part of thefourth layer has been printed directly onto the second layer comprisinga polymeric film, providing the background pattern. In some examples,this background pattern may have formed part of the substrate showinginformation and consequently may be beneath the second layer. FIG. 2cdepicts the scratch-off structure once the surface has been scratchedand the third and fourth layers have been partially removed from thesecond layer, revealing the information (“A car”). Additional scratchingwould result in complete removal of the third layer and overlying fourthlayer, removing the entire opaque circle.

EXAMPLES

The following illustrates examples of the electrostatic ink composition,method of producing a scratch-off structure, scratch-off structures andrelated aspects described herein. Thus, these examples should not beconsidered to restrict the present disclosure, but are merely in placeto teach how to make examples of the electrostatic ink composition andscratch-off structure of the present disclosure.

Materials

Release additive (a fatty acid ester having a plurality of hydroxylsubstituents):

Efka RM 1920 (BASF): a modified hydrogenated castor oil, which containsa mixture of fatty acid esters in the form of glycerides at least aproportion of which are triglycerides.

Resins

Nucrel® 699 (Dupont): a copolymer of ethylene and methacrylic acid, madewith nominally 11 wt % methacrylic acid.

AC-5120 (Honeywell): ethylene—acrylic acid copolymer with an acid numberof 112-130 KOH/g.

Grinding Agent

Aluminium stearate (Sigma-Aldrich)

Carrier Liquid

Isopar L (available form EXXON): an isoparafinic oil.

Charge Adjuvant

VCA (available from Sigma—Aldrich): an aluminium stearate.

Charge Director

NCD: a natural charge director having the components (i) natural soyalecithin, (ii) basic barium petronate, and (iii) dodecyl benzenesulphonic acid, amine salt, with the components (i), (ii) and (iii)being present in the weight ratios of 6.6%:9.8:3.6%.

Over Print Varnishes

Digiguard® Gloss 210 and Digiguard® Gloss 215 (Michelman): a water-basedoverprint varnish

Example 1—preparation of the transparent liquid electrostatic inkcontaining the release additive

A transparent paste (25 wt % solids) was formed by mixing the resinsNucrel® 699 and AC-5120 (ratio of 4:1) with EfkaRM1920 (5-25 wt % of thesolids) and grinding agent (1.5 wt % of the solids in Isopar L. Thepaste was ground in an attritor SO (from Union Process USA) at 25° C.for 24 h to form a concentrated transparent ink paste.

The ground paste was diluted to 2 wt % solids with Isopar L and a chargedirector (5-8 mL of HP Indigo Imaging Agent (such that the chargedirector constituted approximately 0.1 wt % to 0.3 wt % of the solids ofthe electrostatic ink composition) was added to form a transparentelectrostatic ink. The transparent electrostatic ink was left overnightbefore printing.

Example 2—preparation of scratch off structures

Information, in the form of words, letters, images or any combinationthereof, was printed onto a paper substrate (300 g Condat paper) byusing an HP Indigo 7000 printing press to form a first layer showinginformation.

DigiGuard® Gloss 215 (from Michelman, Inc), a transparent varnish, wasapplied over the first layer by using drawdown rod #0 (designed to apply0.2 gsm layer; from Diversified Enterprises, USA), forming a secondlayer overlying the first layer.

The transparent liquid electrostatic ink produced in Example 1 wasprinted over the combined first and second layers by using an HP Indigo7000printing press to form a third layer on top of the second layer,such that the third layer covered at least the portion of the firstlayer showing information.

Finally, a fourth layer, comprising several coloured liquidelectrostatic inks was printed over the third layer by using an HPIndigo 7000 printing press, providing an opaque layer through which theinformation printed on the paper substrate cannot be perceived. In thisExample, the fourth layer comprises 200% black, 200% white and 100%magenta inks (HP Indigo Electrolnk® 4.5).

Comparative Examples—scratch-off structures without varnish layer

Comparative scratch-off substrates were prepared by following theprocedure disclosed in Example 2 omitting the second layer, that is, theDigiGuard® Gloss varnish layer.

Example 3—correlation between scratchability of the image and amount ofrelease additive in the transparent ink

The effect of the amount of the release additive in the transparentelectrostatic ink composition on the scratchability of the transparentelectrostatic ink was examined by scratch testing.

A test was performed by using a Model 551 Shear/Scratch testingapparatus (from Taber®). The printed samples were dried at 80° C. for 4h prior the testing to avoid “slipping” of the scratching needle. Theweight of debris removed by scratching at a pressure of 50 g wasmeasured.

The results of these tests on the scratch-off structures produced inExample 2 and the Comparative Examples are shown in the graph in FIG. 3.By testing several scratch-off structures with different amounts ofrelease additive in the transparent electrostatic ink of the thirdlayer, a clear trend emerges; the scratchability of the third layer,with the fourth layer overlying it being removed simultaneously,increases with increasing amount of release additive. Aboveapproximately 10 wt % release additive, the scratchability levels off,remaining approximately constant for transparent electrostatic inkcompositions with 10-15 wt % release additive

FIG. 3 also shows that the scratchability of the transparentelectrostatic ink composition (third layer) significantly increases whenit is printed on the varnish (second layer) in comparison to printing itdirectly onto first layer.

The results of another method of testing the scratchability of thetransparent electrostatic ink show a comparable trend. In this test, acoin or nail is drawn across a sample at a pressure of approximately 15N to scratch off the third and fourth layers of the scratch offstructure. Sample 1, a reference sample in which the third layer wasomitted, showed a thin, partially incomplete, line where the coin/nailhad removed some of the third and fourth layer. Sample 2, in which 5 wt% release additive was included in the transparent electrostatic inkcomposition of the third layer, showed a thicker line of removed thirdand fourth layers than sample 1. Finally, sample 3, in which 10 wt %release additive was included in the transparent electrostatic inkcomposition of the third layer, showed a thick line of removed third andfourth layers.

Example 4—effect of coat weight of the second layer on scratchability

In these tests, the scratch-off structures tested were similar to thosein Example 1, except that the third layer was omitted, i.e. the fourthlayer, the coloured electrostatic ink layer was printed directly ontothe second layer, i.e. the overprint varnish. These tests were performedbecause 1) the scratch tests of the scratch-off structures including thetransparent electrostatic ink layer, that is, the third layer, using theTaber scratch tester are problematic because of sliding effects due tothe presence of the release additive and low resolution; and 2) it wasan aim to “isolate” the influence of the presence of the varnish, thatis, the second layer, on the scratchability. The results of the testgive an indication of the correlation of the amount of overprint varnishwith the scratchability of electrostatic ink composition printed on theoverprint varnish.

The scratch-off structures used in these test were formed by thefollowing method:

Information, in the form of words, letters, images or any combinationthereof, was printed onto a paper substrate (300 g Condat paper) byusing an HP Indigo 7000 printing press to form a first layer showinginformation.

DigiGuard® Gloss 210 (from Michelman, Inc), a transparent varnish,diluted to 40 wt % solids with water was applied over the first layer byusing a drawdown rod, forming a second layer overlying the first layer.Different drawdown rods were used to achieve different coat weights ofthe varnish. Drawdown rods (from Diversified Enterprises, USA) #0(designed to apply 0.2 gsm layer), #1.5 (designed to apply 0.4 gsmlayer) and #4 (designed to apply 1.5 gsm layer) were used. The coatweight of the DigiGuard® Gloss was determined gravimetrically by using awashable plastic PET substrate.

No transparent liquid electrostatic ink was applied as the third layerand thus, no third layer is present in these scratch-off structures.

Finally, a layer comprising several coloured liquid electrostatic inkswas printed over the second layer by using an HP Indigo 7000 printingpress, providing an opaque layer through which the information printedon the paper substrate cannot be perceived. In this Example, the“fourth” layer comprises 200% black, 200% white and 100% magenta inks(HP Indigo ElectroInk® 4.5).

The scratch-off structures were tested for scratchability as describedin Example 3. The results of these tests are displayed in FIG. 4. Thegraph shows that the scratchability increases with increasing coatweight of the varnish, that is, the second layer, and reaches andoptimum coat weight at approximately 1.5 gsm.

While the composition and scratch-off structure has been described withreference to certain examples, those skilled in the art will appreciatethat various modifications, changes, omissions, and substitutions can bemade without departing from the spirit of the disclosure. It isintended, therefore, that the disclosure be limited by the scope of thefollowing claims. The feature(s) of any dependent claim can be combinedwith the feature(s) of any of the other dependent claims and any of theindependent claims.

1. An electrostatic ink composition comprising a component selected froma fatty acid ester having a plurality of hydroxyl substituents and afatty acid amide having a plurality of hydroxyl substituents.
 2. Theelectrostatic ink composition according to claim 1, wherein theelectrostatic ink is a transparent electrostatic ink.
 3. Theelectrostatic ink composition according to claim 1, wherein thecomponent selected from a fatty acid ester having a plurality ofhydroxyl substituents and a fatty acid amide having a plurality ofhydroxyl substituents constitutes at least 1 wt % of the solids of theelectrostatic ink composition.
 4. The electrostatic ink compositionaccording to claim 1, wherein the component selected from a fatty acidester having a plurality of hydroxyl substituents and a fatty acid amidehaving a plurality of hydroxyl substituents constitutes 30 wt % or lessof the solids of the electrostatic ink composition.
 5. The electrostaticink composition according to claim 1, wherein the component selectedfrom a fatty acid ester having a plurality of hydroxyl substituents anda fatty acid amide having a plurality of hydroxyl substituents comprisesa carbon chain comprising 4 to 40 carbon atoms.
 6. The electrostatic inkcomposition according to claim 1, wherein the component selected from afatty acid ester having a plurality of hydroxyl substituents and a fattyacid amide having a plurality of hydroxyl substituents comprises or isderived from a saturated fatty acid, an unsaturated fatty acid, astraight-chain fatty acid, a branched fatty acid, a cyclic fatty acid ora mixture thereof.
 7. The electrostatic ink composition according toclaim 1, wherein the fatty acid ester is the product of esterificationof a plurality of fatty acids with a polyol, wherein the plurality offatty acids may be the same or different from one another.
 8. Theelectrostatic ink composition according to claim 1, wherein the fattyacid ester is a mono-, di- or triglyceride.
 9. The electrostatic inkcomposition according to claim 8, wherein the fatty acid ester is a di-or triglyceride and each fatty acid chain comprises at least onehydroxyl substituent.
 10. The electrostatic ink composition according toclaim 1, wherein the component selected from a fatty acid ester having aplurality of hydroxyl substituents and a fatty acid amide having aplurality of hydroxyl substituents comprises a hydrogenated castor oil.11. The electrostatic ink composition according to claim 1, furthercomprising: a resin; a carrier liquid; and a charge director, a chargeadjuvant, or both.
 12. The electrostatic ink composition according toclaim 11, wherein the resin is a thermoplastic resin having acidic sidegroups.